


Step Off Into The Deep End

by MugenYumeDansu



Category: Avatar: The Last Airbender
Genre: Accidental Sex, Alternate Universe, Alternate Universe - Modern Setting, Angst, Bending and benders, Breakups, Cute, Developing Romance, Emotional Hurt/Comfort, F/M, First Kiss, First Time, Fluff, Hakoda is not Katara's father, Kya is not Sokka's mother, More tags to be added, Multi, Not sibling incest, Past Abuse, Sexy, Sokka is sweet, Step Siblings, Threesomes, Zuko is Awkward, Zuko lives with Uncle, finding each other, multi-partner sex, mutual comfort, until he isn't
Language: English
Status: In-Progress
Published: 2018-01-27
Updated: 2018-03-09
Packaged: 2019-03-10 08:55:16
Rating: Explicit
Warnings: Underage
Chapters: 2
Words: 4,503
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13498720
Author URL: https://archiveofourown.org/users/MugenYumeDansu/pseuds/MugenYumeDansu
Summary: Everybody is getting broken up with.But it's Sokka's break up with Suki that really starts it.





	1. Chapter 1

Sokka was staring again. He was sitting across the room, trying to watch hockey on the flat screen, but he couldn't drag his eyes away from the scene out on the back porch, through the sliding glass door.

His step sister was out there doing her Tai Chi, while their mutual best friend Zuko was practicing with his duo dao.

This had been a routine for Zuko and Katara since 8th grade when Zuko had finally figured out that he wasn't going to be able to ignore them anymore and just joined their group.

Now it was a common sight most weekends. Zuko would come over to practice martial arts with Katara and Aang, the bald kid who was currently on the other side of the yard meditating.

Meanwhile the last member of their group was sitting on the other side of the couch headphones in, feet propped up on the arm of the couch, bobbing her head along with the beat of whatever it was she'd taken an interest in this month.

And this left Sokka sitting there watching hockey and grousing every time his team got scored against or didn't make a shot.

Or he would have been if he wasn't currently staring at his step sister's ass and legs in those stupid blue work out pants, and her breasts, in that stupid silver tank top.

Sokka was completely fucked.

He had been developing this little crush ever since he had accidentally walked in on her getting out of the shower and gotten an eye full. It was the same night that Suki had broken his heart. He had also gotten a black eye from the shampoo bottle she'd chucked at him, but that didn't stop him from remembering every detail later that night. He'd jerked off twice to it before going to sleep. And he felt guilty about it the whole time. Suki had just left him and here he was jerking off to images of his step sister.

Now he was always sneaking glances, and he had a nice stockpile of images for the spank bank. But deep down it kind of made him wonder just how sick he was. Katara was his step sister, and she trusted him.

It didn't help much that Sokka knew for a fact that Zuko had it bad for Katara too. Not that he had made his interest clear. Sokka was pretty sure that Zuko still wasn't sure what it was yet.

And Sokka could admit that Zuko wasn't bad looking. Aside from the scar covering the left side of his face, he was actually pretty damn good looking. So Sokka was pretty sure that Katara would eventually pick up on Zuko's crush and then the two would end up being an item.

Which, Sokka didn't really mind, from a brotherly standpoint. But for the last year he hadn't really been thinking about Katara from a brotherly standpoint.

Guilt twisted in his gut again. Sighing Sokka turned back to the tv.

 

* * *

 

 

_Sokka trudged home, his whole heart aching._

_Suki had broken up with him. Apparently she had met someone and they had hit it off. Now Sokka was on his own._

_It hurt because he truly had cared for Suki. And now she was gone._

_He shuffled through the door, and up the stairs, so caught up in his shitty thoughts that he didn't notice Katara trying to get his attention until she reached up a yanked him back by his sleeve. He let out a started "Wha?" before realizing who had grabbed him._

_"I asked if you were ok? You look like someone kicked your puppy. Did you and Suki have a fight?" Katara's face was scrunched up in concern and her hand lingered on his arm. Sokka felt a little numb._

_"No, we didn't fight. She broke up with me." He practically snapped. Katara's eyes went wide and one hand flew up to cover her mouth._

_"Oh, Sokka, I'm sorry." She said sincerely._

_And the dam broke. Tears Sokka didn't know we're pricking his eyes fell and he actually cried._

_Katara reached out and pulled him into a hug._

_They had ended up sitting on the couch hugging while Sokka reigned in his emotions and calmed down._

_For hours Katara sat there and talked to him, rubbing soothing circles on his back. Eventually, exhausted from the emotional outburst he'd just gone through, Sokka started drifting off, so Katara had draped a throw blanket over him and left him to rest._

_Later that night Sokka had woken up to his bladder protesting it's fullness._

_He stumbled through the house, half asleep to the bathroom door and opened it._

_In his haste to get to the toilet he had failed to hear the shower shutting off or the shower door sliding open. When the door swung open a very naked, very wet Katara was stepping out of the shower to grab her towel._

_For a second both of them stood frozen, wide eyes and confused. Sokka's eyes took in the expanse of glistening mocha skin, high perky breasts with dusky nipples, peaked from the temperature difference, flat stomach, wide hips, and a nest of chocolate curls at the Apex of smooth thighs._

_He felt the blood rushing to his face and... Other parts of his anatomy a split second before Katara shrieked, grabbed her towel to her chest and snatched up something from behind her and threw it full force at his face._

_Pain exploded across the right side of his face on contact and he grunted in pain and stumbled back, shouting an apology behind him and taking off across the house to his room, aching bladder temporarily forgotten._

_He avoided her for the rest of the night, but the images of her in all her naked, soaking wet glory stuck in his head._

 

* * *

 

 

Sokka opened the door and walked in, heading for the bathroom for a shower after soccer practice. He had grass and mud all over him and he wanted nothing more than to spend an hour soaking in the hot water after a hard day's practice.

"Hello! Anyone home?" He called out, as was his habit. It was just him and Katara for the next few nights, as Dad was out working on a fishing boat, and Kya's mother had come down sick and she was staying with her until she got better.

No answer so Katara wasn't home yet.

Sokka dropped his gear in his room and went to the kitchen to sit something out for dinner. It was Sokka's turn to cook tonight so it was frozen pizza again.

He took a meat lovers out of the freezer and set it on the counter to thaw a little. He would come back after his shower and pop it in the oven.

He headed upstairs to the bathroom and shut the door, locking it as had become habit since 'The Incident'.

He stripped down and threw his dirty gear in the hamper and turned on the shower. He had just stepped into the spray when he heard the front door slam and Katara run up the stairs. Her bedroom door slammed too, startling Sokka. Katara never slammed doors, so something must be wrong.

Sokka quickly scrubbed himself down, forgoing his usual routine of rubbing one out in the shower.

He shut off the water and toweled off fast. He hadn't brought any clothes other than a pair of boxers into the bathroom with him so he donned them and then wrapped the towel around his waist for extra coverage and opened the door.

Padding barefoot down the hall, Sokka jumped like a rabiroo when Katara's door was jerked open. She was standing there with her hair dishoveled and her eyes puffy and red. She'd been crying.

Sokka forgot about only being in his boxers. He reached out and pulled her over, hugging her. She wrapped her arms around his naked torso and shoved her face into his shoulder, sobbing.

"Shh, shh, it's ok." He propped his chin on top of her head and rubbed her back. They stood there for quite some time until Katara had calmed down as much as she could. Sokka leaned back, rubbing his hands up and down her arms to keep her calm.

"What happened? Why are you crying, Kat?" He asked gently, brows furrowed in concern.

"Jet... I broke up with Jet. I caught him cheating on me." She sniffled hard, her arms coming up to wrap around her middle.

Oh. The asshole that Katara had been dating for about a month now. Anger spiked in Sokka's chest.

"Do you want me to go beat his ass? I'm pretty sure Zuko might help me." Sokka asked, keeping as calm as he could manage. He had tried to warn her when she had first started dating him, but Katara was stubborn. Now Sokka wished she had listened to him. It hurt his heart, seeing her upset like this. 

Katara shook her head.

"Zuko offered too, but right now I just want to forget I ever dated that asshole. I feel sick." She told him, a shiver of revulsion going through her. Something clicked in Sokka's head then.

"Katara, you didn't... You didn't sleep with him did you?" He asked, a little disgusted. Katara's eyes snapped up to meet Sokka's and he saw the truth in her eyes. A fresh wave of tears flooded her. Sokka pulled her back to his chest and held her, rocking slightly and shushing her.

"I'm sorry. I'm sorry Sokka, I'm so stupid," Katara was saying through her sobs. "He told me he loved me. And I believed him." She broke down, leaning completely on Sokka.

After a few minutes Katara was able to calm herself down again. Sokka gently guided her into her room and sat down with her on the bed. She still clung to him like a lifeline.

"Do you want to talk about it?" Sokka asked after a while.

"No," Katara groused. "And yes." She gave in a little.

"You don't have to. But just know I'm here." He promised her.

"No I think I need to tell someone. I haven't even told Toph." She sighed, heavy and sad.

"Ok." He sat there patiently while she worked up the courage.

"Remember when we went to that stupid dance?" At his nod she continued. "Well it was after that, we were hanging out at his house and we were down in the basement, watching a crappy romcom. And he kissed me. At first it was sweet, and then he put his hand up my skirt, and I told him I wasn't ready. He told me he loved me, and if I loved him too then I was ready. I didn't really want to, but... I just let him lift my skirt and..." She choked up a little.

"It's ok, I can figure out the rest." Sokka told her. He was extremely pissed off, and he wanted nothing more than to go hunt down the creep who had hurt his Katara, and beat him senseless, but right now Katara needed him.

"Oh Gods, Sokka, I feel dirty. Like I'm ruined." She mumbled into his bare chest. He ignored the feeling of his nipple perking from her breath and hugged her tighter.

"I know. But you're not, ok. He took advantage of you, but he's just a creep. Not all men are like that." He consoled.

"I know. You're not like that. You wouldn't do that to anyone. Neither would Aang. Or Zuko." She replied. Sokka's heart twisted.

"No, we wouldn't." He confirmed, pushing her off his chest and looking her in the eye. They locked eyes. Hers were clear and he could see that she believed him. A small smile flitted across her face.

"Thank you Sokka. You're the best, you know." She tucked a strand of her wild hair behind her ear. It escaped again immediately, and Sokka's hand came up and brushed it back without thinking. His fingers lingered, smoothing her hair down. When he looked back at her face there was something else there.

Her lips were parted, her tongue darting out to swipe over the bottom one. Her eyes had clouded a little and her eyes darted down and then back up to Sokka's eyes. 

He was confused for a second, and then Katara leaned forward and pressed her lips to his. Shock bolted through him and he froze for a second. And then instinct took over and he kissed her back, the hand that had smoothed her hair now molded to the side of her face as his lips moved against hers.

Her mouth opened and he shoved his tongue inside, tasting and exploring. She moaned and clutched at his sides, pulling him closer. He slid his tongue against hers, setting off little sparks in their wake. She moaned again and pushed back against Sokka's chest, climbing into his lap.

It was when her clothed ass rubbed against his very not clothed erection that his brain kick-started and he pulled back, eyes wide.

"Oh shit." He mumbled. Katara's eyes shot down to where the towel had dropped to the bed and his manhood was free standing from the slit in his boxers, precum leaking from the tip. With a sick sense of curiosity he wondered how Katara was going to react. 

She shocked him when she reached down and wrapped her fingers around him and stroked once.

He hissed at the bolt of pleasure that shot up his spine. Katara licked her swollen lips again and looked up at him.

"You're bigger than Jet." She said as nochalantly as could be.

"We shouldn't." Sokka met her deep blue eyes and told her. She nodded.

"I know. Do you want this?" She asked. He swallowed hard around the lump forming in his throat and nodded.

"Can I tell you something?" She looked up, eyes hooded.

"Hmm?" He couldn't seem to form actual words.

 "I've been imagining what it would be like since the day you saw me naked." She almost whispered. He choked a little. Her fingers squeezed him again and his hips rolled, his cock slipping through her fingers.

"Ungh, r-really? I have too. Gods I've felt like such a creep, wanting to fuck my sister." He confessed, rolling his hips again. 

"Technically I'm your step sister, so there's no blood ties. Do you want to? I kinda want you to." She told him, her fingers pumping him. Precum was dribbling down onto his thigh now.

He moaned and grabbed her hips, slamming his mouth back down on hers. She lost her grip on his cock but he didn't care. He kissed her for all he was worth. When they pulled back he slid his hands up her stomach, dragging her shirt up.

"I want to see you naked again. Please." He told her, she helped him pull her shirt up over her head and drop it on the floor. He cupped her breasts and pulled the bra down, leaning forward and flicking his tongue against her nipple. She gasped and let out a high moan. So he sucked the whole thing into his mouth and played with it with his tongue and teeth.

Her hands flew to the back of his head, holding him in place. He slid his hands back and unhooked her bra and dragged it down. He moved to the other breast and did the same, squeezing and kneading the other with one hand.

He let her nipple slide out of his mouth with a pop and dragged her bra completely off, dropping it with her shirt.

He kissed his way down her stomach, slowly leaning her back on the bed. He undid her jeans and dragged them down over her hips.

When he dragged her blue panties down he was shocked to find her shaved completely bare.

She shifted a little.

"Jet... Said guys like this better." She explained. Sokka growled.

"S'fuckin hot." He said right before he licked a hot swipe through her lips. She cried out and her hips bucked. Sokka held her hips down and spread her labia with one hand and then slowly slid his tongue along her slit.

He pressed against her clit and licked hard. Katara was mewling above him, fingers digging into the bed.

"Katara, can I make you cum like this?" He asked, sliding a finger along her entrance and dipping into her a little.

"Yes! Please!" She begged, her eyes glazed over with lust.

Sokka delved in, kissing and licking, undulating his tongue against her clit over and over, and then sucking hard. Katara was moaning constantly now, her thighs shaking and her hips fighting to keep still and rock into the pleasure at the same time.

Sokka slid his fingers into her heat and pumped slowly while his mouth dragged very vocal responses from the girl above him.

Suddenly she keened and her hips started snapping back and forth. Sokka sucked hard on her clit, fingers scissoring inside her as she came hard, a rush of fluid coating his fingers and chin.

He pulled away, licking his fingers clean and wiping his face on the blanket. He dropped his boxers and crawled up the bed, laying beside his quivering lover. She turned her head and kissed him again.

"That was the first time anyone's done that." She whispered, breathless.

"Good. I'm glad I got to be the first one to taste you. You taste good. Like the ocean." He told her. She blushed harder than she already was.

"Are you still gonna...?" She left the sentence unfinished.

"Yes, I was giving you a minute. But if you want to rush then fine." He rolled over her, and she opened her legs to accommodate him. He lined himself up with her opening and pushed the head in slowly. She hissed, and he stopped.

"Told you you were bigger than Jet. It just kinda stings. You can keep going." She told him. His arms wrapped around her and he started pushing again.

"You tell me if I hurt you, ok? Promise me Katara. I don't want to hurt you." He locked eyes with her. She nodded quickly. Sokka's head dropped to her shoulder and he rocked his hips until he was sheathed completely inside her.

He pulled out and pushed back in, her head flew back, a moan forming in her throat. He worked himself in and out until he got into a rhythm, Katara moaning and clutching at his sides, his ass, everywhere she could reach.

"Harder Sokka. It feels good!" She mumbled between noises. His hips snapped into hers hard, jerking her whole body forward a little. Sokka was afraid he'd hurt her until she made a decidedly pleased noise. So he did it again, a little harder. She whimpered and shuddered. So he kept going, getting a little harder each time he thrust.

She was getting close, he could feel it in the way she was moving, and breathing. He leaned back and lifted her hips up onto him, slamming into her hard. The new angle set her off and her back arched. She let out a scream and came again, harder than the first.

Sokka felt it coming on fast, his spine tightening.

"Katara, I'm going to cum. I'm going -to...Unghhh!" He jerked his hips up into her until he was on the razor's edge and jerked out of her, his fist pumping him hard and fast. Thick ropes of cum pulsed from the head and landed arcoss her belly, Stark white against mocha brown. He kept going until he was too sensitive to touch. He dropped beside Katara, spent.

 

* * *

 

Sokka woke up a couple of hours later to Katara pumping him in her hand.

"Fuck, Katara!" He mumbled into her pillow, curling his hips into her grip.

"Fuck me Sokka. From behind. Please." She asked. He nodded, biting his lip. She let go and rolled over, pushing her ass Into the air. Sokka got up and moved around behind her. He lined up with her entrance.

"You sure?" He confirmed.

"Yes, and do it hard. I liked the way you did it earlier. I want you to make me cum again." She told him, sweeping her tousled hair over her shoulder and glancing back. "Jet only made me cum once, and it was nothing like this."

"Alright. By the way you're fucking hot like this." He said, slipping into her without another word. She moaned again.

He did as she asked and started out slow but built to a fast pace quickly. He was slamming into her, her ass jiggling with every thrust, and she was moaning and slamming back into him.

"Fuck Sokka, yess... God you feel so good. Yes... Yesss... Ah, ah, yeah!" A litany of praises fell from her lips. She sized up and came suddenly, squeezing his cock hard inside. He kept pumping through her orgasm and she came again within a few thrusts.

He was getting close now, and he knew it wasn't going to last much longer, so he grabbed her hips in both hands and slammed her back on to him, fucking into her frantically. She was almost screaming now, and she came again, hard just as he felt himself tipping over he edge. He pulled out and jerked himself off hard, covering her ass in cum. As soon as he was finished he leaned back, out of breath and staring down at his seed covering his sister's ass.

He reached out and ran a finger though a rivulet of rapidly cooling semen. He leaned up and put his fingers to Katara's lips. She looked him in the eye, opened her mouth and licked his fingers clean. If he hadn't just cum harder than he ever remembered in his life, he would have right there on the spot.

 

* * *

 

The rest of their week went by the same way. During the day Aang, Toph and Zuko we're at the house, playing games, goofing around and hanging out. After everyone left, Katara would initiate sex with Sokka. After he accidentally came inside her once he went and bought some condoms at the drug store, and they went through almost a whole box in two days. The next time Sokka made sure to buy 2 boxes.

It was good, until Kya came back home from Gran-Gran's.

After that they had to sneak around and be a lot more careful.

They figured out a pattern. Kya worked nights at the hospital, so they would wait until she went to work and then end up in one room or the other.

During the day when the others were around they were careful, not showing any signs of what was going on between them. And it continued on that way for three months. And then they tapered off a little, as school had started. It was Sokka and Zuko's senior year, Katara's Junior, and Aang and Toph's Sophomore.

Sokka and Katara couldn't meet up most nights, with school and everything else going on.

But what they felt for each other was still there. Whenever they found a moment alone they were all over each other.

And then Gran-Gran got sick again. Hakoda was home on one of his weeks off the week before, and had just left. Kya had been at Gran-Gran's for two days, and then suddenly Sokka and Katara were alone again.

It was during one of the nights that Sokka and Zuko had been at soccer practice, and they had come to Sokka's place to study. They had decided to order something to eat after they got showered and cleaned up.

Zuko had just finished his shower and was leaving the bathroom dressed in a borrowed pair of Sokka's pajama pants. He was padding down the hallway when he heard a noise from Katara's room.

Her door was cracked and Zuko caught a glimpse of Katara and Sokka. They were kissing, Sokka holding Katara close, her arms wrapped around him. Zuko's jaw dropped. His cheeks heated up. Just then they broke apart.

"I've gotta go, Zuko will be out of the shower soon. I'll come tonight after he goes home, ok?" Sokka whispered.

"Ok. Go ahead before we get caught." Katara pushed her brother towards the door.

Zuko shook his head and quickly made his way to Sokka's room.

He had just plopped down on the bed when Sokka opened the door. Zuko almost missed the momentary panic in Sokka's eyes. He would have if he hadn't been looking for some kind of reaction.

"Yo, you hungry?" Sokka asked. Zuko didn't trust himself to speak so he nodded.


	2. Chapter 2

Zuko had mulled it over in his head over and over again. He was uncomfortable at first after finding out about Katara and Sokka's secret relationship.

He had played it off and made sure neither of them knew that he knew. It stung, because he had had feelings for Katara for quite some time now. But he knew he didn't have a chance now.

And it was her own _brother_ that she was with. It bothered Zuko. He couldn't figure out when it had started, or how, but it made his stomach turn.

And then it didn't.

It started to change when his dreams started featuring Katara and Sokka. Together.

Not to long after that Zuko started noticing things about Sokka. Things he didn't notice about other boys because he had always been interested in girls.

And then the weirdness cranked up to a whole new level. Zuko started having to fight off the same reactions he sometimes had around Katara during soccer practice, and just hanging out with Sokka alone.

And then the night came that it all sort of exploded in his face.

 

* * *

 

 

Sokka had invited Zuko over that weekend for 'guy time' as he called it. No one else was around. Katara was with Toph, and their parents were working. It had started raining just a few hours before, and it wasn't bad, but it was getting worse.

They had been in the middle of a movie marathon when Sokka turned to Zuko.

"So, the main girl is totally hot, right?" He asked. Zuko didn't know how to respond, as he hadn't been paying much attention. He had been staring at Sokka, who was sitting there in a pair of pajama pants and no shirt. He was well built, if thin. But Zuko was pretty thing too. Both of them were tall and a little on the slender side. And between the martial arts training, the soccer and the other physical things they did, both of them had some pretty defined muscles.

And Zuko had been sitting there staring at Sokka's bare chest and abs for almost an hour now.

"Uh, yeah, I guess. Not really my type." Zuko replied, pulling the non-answer out of his ass when he realized that Sokka actually expected him to reply.

(TBC)

**Author's Note:**

> Zuko is 18, Sokka is 18, and Katara is 16.


End file.
